SU-FF-T-144: Determination of Feasibility and Prescribed Dose for 142Pr Glass Seeds for Prostate Cancer Brachytherapy

Abstract

Purpose: A glass seed is proposed for brachytherapy treatment of prostate cancer. A prescribed dose for was derived and case study performed to assess the feasibility of the seed. Method and Materials: Sensitivity studies using the linear-quadratic model and biological parameters were conducted to find the prescribed dose for . A case study was performed to assess the feasibility of the seed and modeled using the VariSeed™ program. The main work was the description of the seed, optimized planning, and comparison with conventional seeds. Results: 90 Gy from can give the equivalent biological effective dose (BED) of 144 Gy from and 125 Gy from using reasonable assumptions. As the α/β ratio decreases, the BED for increases exponentially. The BED of was insensitive to the tumor repopulation factor. Therefore, is acceptable for treating tumors with high tumor repopulation factor and low α/β ratio. Based on the dose-optimization planning, the best arrangement of seeds, dose coverage, and isodose contours were found using glass seeds with the initial activity of 6 mCi. Fifty seeds can deliver the prescribed dose to about 90% of the prostate volume satisfying the dose constraints rules which were set to give lower dose to adjacent organs. From the comparisons, the coverage of glass seeds was higher than that of typical seeds. The surface area of the rectal wall exposed by glass seeds was less than that by seeds. Conclusion: A prescribed dose of 90 Gy is suggested for . glass seeds can deliver the prescribed dose to a larger volume of the prostate and the undesired doses to adjacent organs were less than seeds using low energy photons.